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Immunoradiometric assay of circulating C-reactive protein: age-related values in the adult general population
W L Hutchinson1, W Koenig, M Fröhlich
1Immunological Medicine Unit, Division of Medicine, Imperial College School of Medicine, Hammersmith Hospital, London W12 0NN, United Kingdom.
Insights
Elevated C-reactive protein (CRP) levels below 5 mg/L indicate increased risk for cardiovascular events and are significant in osteoarthritis and neonatal infections. This study establishes new reference ranges for CRP.
Area of Science:
- Clinical Chemistry
- Immunology
- Epidemiology
Background:
- Increased C-reactive protein (CRP) values, even below 5 mg/L, are linked to higher risks of atherothrombotic events.
- Clinically significant elevated CRP levels are observed in osteoarthritis and neonatal infections.
- Sub-5 mg/L CRP ranges were previously considered within normal limits but are now recognized as clinically relevant.
Purpose of the Study:
- To develop a robust assay for measuring C-reactive protein (CRP) across a clinically relevant range.
- To establish reference values for CRP in large adult populations.
- To investigate the relationship between CRP levels, age, and sex.
Main Methods:
- Development of a new polyclonal-monoclonal solid-phase immunoradiometric assay (IRMA) for CRP.
- Assay validation with a measurement range of 0.05-10.0 mg/L.
- Analysis of plasma CRP values in adult populations from Germany and Scotland.
Main Results:
- Plasma CRP values were similar between German and Scottish adult populations.
- Median CRP levels approximately doubled with age, increasing from 1 mg/L to 2 mg/L across age decades.
- CRP levels tended to be higher in females compared to males.
Conclusions:
- This study provides the largest dataset to date for C-reactive protein (CRP) reference values.
- The findings offer valuable reference information for future clinical and epidemiological research.
- The data supports the clinical significance of CRP levels previously considered within the normal range.
Background:
: Increased values of C-reactive protein (CRP), the classical acute phase protein, within the range below 5 mg/L, previously considered to be within the reference interval, are strongly associated with increased risk of atherothrombotic events, and are clinically significant in osteoarthritis and neonatal infection.
Methods:
: A robust new polyclonal-monoclonal solid- phase IRMA for CRP was developed, with a range of 0.05-10.0 mg/L.
Results:
: Plasma CRP values in general adult populations from Augsburg, Germany (2291 males and 2203 females; ages, 25-74 years) and Glasgow, Scotland (604 males and 650 females; ages, 25-64 years) were very similar. The median CRP approximately doubled with age, from approximately 1 mg/L in the youngest decade to approximately 2 mg/L in the oldest, and tended to be higher in females.
Conclusion:
: This extensive data set, the largest such study of CRP, provides valuable reference information for future clinical and epidemiological investigations.